Magnetic core and magnetic component

ABSTRACT

In a magnetic core including a core assembly having a structure that multiple thin strip blocks are arranged, the thin strip blocks being formed of multiple laminates of nanocrystalline thin strips made of a nanocrystal-containing alloy material, the thin strip block includes a fixedly joined portion in which the nanocrystalline thin strips adjacent to each other in a lamination direction are fixedly joined together. The fixedly joined portion may include side surfaces of the nanocrystalline thin strips and may be a laser welded portion.

CLAIM OF PRIORITY

This application is a Continuation of International Application No.PCT/JP2021/032510 filed on Sep. 3, 2021, which claims benefit ofJapanese Patent Application No. 2020-151207 filed on Sep. 9, 2020. Theentire contents of each application noted above are hereby incorporatedby reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a magnetic core and a magneticcomponent including the magnetic core.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2017-141508discloses a heat treatment apparatus for a laminate of amorphous alloythin strips, the heat treatment apparatus including a lamination jigthat holds the laminate of the amorphous alloy thin strips, two heatingplates that sandwich the laminate from upper and lower surface sides ina lamination direction without contacting the lamination jig, and aheating control device that controls heating and temperature of the twoheating plates. By heat-treating the laminate of the amorphous alloythin strips with the disclosed heat treatment apparatus, a magnetic coreincluding a laminate of thin strips made of a Fe-based nanocrystallinealloy can be obtained.

International Publication No. 1999/21264 discloses a laminated core fora motor, the core including multiple magnetic plates laminated one aboveanother and being provided with magnetic poles each having an unevensurface that includes ridges and grooves alternately formed along adirection of rotation of the motor, wherein fixedly joined portions ineach of which the magnetic plates are fixedly joined together are formedin surfaces of the grooves formed in the magnetic poles.

SUMMARY OF THE INVENTION

When the laminate of the amorphous alloy thin strips, disclosed inJapanese Unexamined Patent Application Publication No. 2017-141508, areheat-treated, heat generates due to crystallization of the amorphousalloy thin strips. Unless the generated heat is properly controlled,magnetic characteristics of the obtained laminate of the thin stripsmade of the nanocrystalline alloy (called a laminate of nanocrystallinethin strips) may not be properly improved, or thermal runaway may occur,thus causing burning of the thin strips in some cases. The number of thelaminated thin strips in the laminate of the amorphous alloy thin stripsis related to the heat generated in the laminate during the heattreatment and is also deeply related to magnetic characteristics of themagnetic core including the laminate. Accordingly, when laminatesdifferent in the number of the laminated thin strips are prepared toobtain multiple types of magnetic cores with different magneticcharacteristics, heat treatment conditions need to be set individuallyfor each of the laminates. If the amorphous alloy thin strips areheat-treated in a state separated one by one instead of heat-treatingthe laminate in bulk, the nanocrystalline thin strips obtained with theheat treatment are difficult to handle because of being brittle, anddamages, such as cracking and chipping, are likely to occur in a step oflaminating the nanocrystalline thin strips one above another. This givesrise to a problem in the viewpoint of ensuring the quality of themagnetic core.

The present invention provides a magnetic core having a structure thatnanocrystalline thin strips are laminated one above another and havingeasily stabilized magnetic characteristics. The present inventionfurther provides a magnetic component including the magnetic core.

According to one aspect, the present invention provides a magnetic coreincluding a core assembly having a structure that multiple thin stripblocks are arranged, the thin strip blocks being formed of multiplelaminates of nanocrystalline thin strips made of ananocrystal-containing alloy material, wherein the thin strip blocksinclude fixedly joined portions in each of which the nanocrystallinethin strips adjacent to each other in a lamination direction are fixedlyjoined together.

Since the core assembly (core stack) can be fabricated by preparing thethin strip block made up of the nanocrystalline thin strips laminatedone above another, and by arranging a multiple number of the thin stripblocks. Therefore, failures, such as damages, are less likely to occurin the nanocrystalline thin strips than in the case of forming alaminated core by laminating the nanocrystalline thin strips one by one.As a result, the quality of the magnetic core obtained by covering thecore assembly with an impregnated coating can be increased.

When the core assembly is constituted along the lamination direction ofthe nanocrystalline thin strips in the thin strip block, a direction(array direction) in which the multiple thin strip blocks are arrayed isalong a direction (lamination direction) in which the multiplenanocrystalline thin strips forming the thin strip block are laminated,and the core assembly has a structure that many nanocrystalline thinstrips are laminated one above another as in the related-art laminatedcore. However, the core assembly is different from the related-art corein including multiple portions (thin strip blocks) in each of which apredetermined number of the nanocrystalline thin strips are integratedby the fixedly joined portion.

Because of the core assembly being an assembly of the thin strip blocksas described above, even when the fixedly joined portions of the thinstrip blocks are formed by welding, for example, and have electricalconductivity, a short circuit path in the magnetic core including thecore assembly is divided for each of the thin strip blocks. Whenmultiple thin strips are integrated by welding, for example, asdisclosed in International Publication No. 1999/21264, the obtainedmagnetic core is formed as a unit integrated electrically as well, and ashort circuit path in the magnetic core is long. As a length of theshort circuit path increases, an eddy current loss in the magnetic corealso increases. Thus, the iron loss, particularly the eddy current loss,is less apt to increase in the magnetic core according to the presentinvention in which the short circuit path is divided in units of thethin strip block.

A relationship between a direction in which the thin strip blocksforming the core assembly are arrayed and a direction in which thenanocrystalline thin strips are laminated in the thin strip block isoptional. The array direction and the lamination direction may be thesame or different.

In the above-described magnetic core, the fixedly joined portion mayinclude side surfaces of the nanocrystalline thin strips. This makes iteasier to visually recognize the fixedly joined portion and to check afixedly joined state of the thin strip block.

In the above-described magnetic core, the fixedly joined portion may bea laser welded portion. Since the nanocrystalline thin strips arefixedly joined stably in the thin strip block, ease in handling the thinstrip block is increased, and failures, such as damages, are less likelyto occur during a step of arranging the thin strip blocks to fabricatethe core assembly.

In the above-described magnetic core, the nanocrystalline thin strip maybe a member obtained by nano-crystallizing an amorphous thin strip madeof an amorphous alloy material with heat treatment. In this case, thethin strip block preferably has a thickness at which the amorphous thinstrip can produce the nanocrystalline thin strip with the heattreatment. If the thickness of the thin strip block is too large, thereis a concern that temperature control may be disabled in the heattreatment of the amorphous thin strips and that burning of the thinstrip block may occur. In practice, the thickness of the thin stripblock is preferably 3 mm or less in some cases from the viewpoint ofease in control of the heat treatment of the amorphous thin strips.

In the above-described magnetic core, a nanocrystal contained in thenanocrystalline thin strip may have a bcc-Fe phase as a main phase. Withan effect of random magnetic anisotropy due to the nano-crystallization,good soft magnetic characteristics can be obtained while high saturationmagnetic flux density is ensured.

In the above-described magnetic core may include a shift-arranged thinstrip block group made up of the multiple thin strip blocks arrayedalong a first direction, the group including a portion in which thefixedly joined portions of the multiple thin strip blocks are notaligned in the first direction. A practical example of the firstdirection is a thickness direction of the nanocrystalline thin strip.The fixedly joined portion has different magnetic characteristics fromother portions in some cases. Even in those cases, uniformity inmagnetic characteristics of the magnetic core including the coreassembly can be improved depending on the case by arranging the thinstrip blocks such that the fixedly joined portions included in the coreassembly are not aligned in one direction.

In the above-described magnetic core, the core assembly may be coveredwith an impregnated coating. When the core assembly is covered with theimpregnated coating, a failure of peeling-off of the thin strips fromthe core assembly is less likely to occur.

According to another aspect, the present invention provides a magneticcomponent including the above-described magnetic core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view illustrating a magnetic core according toan embodiment of the present invention;

FIG. 1B illustrates a core assembly included in the magnetic coreillustrated in FIG. 1A;

FIG. 2A illustrates a thin strip block included in the core assemblyillustrated in FIG. 1B;

FIG. 2B is a plan view of the thin strip block;

FIG. 3A illustrates an example of a fixedly joined portion formed in thethin strip block when cutting and welding of a thin strip laminate areperformed at the same time (namely, in the case of fusion cutting);

FIG. 3B illustrates another example of the fixedly joined portion formedin the thin strip block when parts of cut surfaces of the thin striplaminate are welded to each other;

FIG. 4A illustrates one modification of the core assembly included inthe magnetic core according to the embodiment of the present invention

FIG. 4B illustrates another modification of the core assembly includedin the magnetic core according to the embodiment of the presentinvention;

FIG. 4C illustrates still another modification of the core assemblyincluded in the magnetic core according to the embodiment of the presentinvention;

FIG. 5 is a flowchart illustrating one example of a manufacturing methodfor the magnetic core according to the embodiment of the presentinvention;

FIG. 6 is a flowchart illustrating another example of the manufacturingmethod for the magnetic core according to the embodiment of the presentinvention;

FIG. 7 is a flowchart illustrating still another example of themanufacturing method for the magnetic core according to the embodimentof the present invention;

FIG. 8A is an explanatory view of a manufacturing process for a hoopmaterial made of a ribbon of amorphous thin strip to formnanocrystalline thin strips included in the magnetic core according tothe embodiment of the present invention;

FIG. 8B is an explanatory view illustrating a configuration of the hoopmaterial made of the ribbon of amorphous thin strip and manufactured bythe manufacturing process illustrated in FIG. 8A;

FIG. 8C is an explanatory view illustrating a stamped section of thehoop material made of the ribbon of amorphous thin strip, illustrated inFIG. 8B;

FIG. 9A illustrates a coupled laminate that is obtained after dividingthe hoop material made of the ribbon of amorphous thin strip,illustrated in FIG. 8B, into smaller parts;

FIG. 9B is an explanatory view of heat treatment of the coupled laminateillustrated in FIG. 9A;

FIG. 9C illustrates an arrangement of heat treatment apparatuses used inthe heat treatment illustrated in FIG. 9B;

FIG. 10A is an explanatory view illustrating a modification of the heattreatment of the coupled laminate illustrated in FIG. 9B;

FIG. 10B is a plan view illustrating a shape of a heat reservoir used inthe heat treatment illustrated in FIG. 10A;

FIG. 11A is a plan view illustrating an example of a thin strip blockmanufactured by the manufacturing method illustrated in the flowchart ofFIG. 7 ;

FIG. 11B is an explanatory view illustrating a fixedly joined portion ofthe thin strip block illustrated in FIG. 11A;

FIG. 12A is a plan view illustrating a shape of an amorphous thin stripto form a core assembly included in a magnetic core according to anotherembodiment of the present invention;

FIG. 12B illustrates a shape of a thin strip block formed using theamorphous thin strip illustrated in FIG. 12A;

FIG. 13A illustrates a ring assembly including the thin strip blockseach illustrated in FIG. 12B;

FIG. 13B illustrates a core assembly obtained by further combining thering assemblies each illustrated in FIG. 13A; and

FIG. 14A is an external view of a motor that is an example of a magneticproduct in which a magnetic component including the magnetic coreaccording to the embodiment of the present invention is used;

FIG. 14B is an external view of a rotor that is one of magneticcomponents included in the motor illustrated in FIG. 14A;

FIG. 14C is an external view of a stator that is another one of themagnetic components included in the motor illustrated in FIG. 14A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings. In the following description, the samemembers are denoted by the same signs, and duplicate description of themembers that have been explained once is omitted as appropriate.

FIG. 1A is a perspective view illustrating a magnetic core according toan embodiment (first embodiment) of the present invention. FIG. 1Billustrates a core assembly included in the magnetic core illustrated inFIG. 1A. FIG. 2A illustrates a thin strip block included in the coreassembly illustrated in FIG. 1B. FIG. 2B is a plan view of the thinstrip block.

As illustrated in FIG. 1A, the magnetic core 100 according to the firstembodiment has the shape of a motor stator. More specifically, themagnetic core 100 includes a cylindrical body portion 10 with athrough-hole 20 passing a center axis along a Z1-Z2 direction, andmultiple teeth 30 extending radially from an outer side surface of thecylindrical body portion 10 (in a direction within an XY plane). Themagnetic core 100 illustrated in FIG. 1 includes twelve teeth 30, andeach of the teeth 30 has a distal end portion 40 with a protrusionprotruding in a circumferential direction and positioned at an outer endof the teeth 30.

The magnetic core 100 is obtained by forming an impregnated coating onthe core assembly 50, illustrated in FIG. 1B, which is in the form of asoft magnetic body. The impregnated coating is formed by applying acoating material, provided as a resin material, to adhere to a surfaceof the core assembly 50, thus making the surface impregnated with theresin material. The coating material is made of, for example, epoxyresin. A thickness of the impregnated coating is set such that theimpregnated coating properly covers the core assembly 50 being aconductor and gives the magnetic core 100 with appropriate insulation.In an example not intended to impose any limitations, the thickness ofthe impregnated coating is from 0.1 μm to 5 μm.

The core assembly 50 is composed of multiple thin strip blocks 51. Thecore assembly 50 illustrated in FIG. 1B is constituted by a laminate offive thin strip blocks 51, 52, 53, 54 and 55 laminated in the Z1-Z2direction.

The thin strip block 51 is a laminate of multiple nanocrystalline thinstrips 511. The nanocrystalline thin strips 511 are made of ananocrystal-containing alloy material. The thin strip block 51illustrated in FIG. 2A is a laminate of a number n of thenanocrystalline thin strips 511 laminated in the Z1-Z2 direction. Asillustrated in FIG. 2B, a shape of the thin strip block 51 in the planview (when viewed from the Z1-Z2 direction) is similar to that of themagnetic core 100. More specifically, the thin strip block 51 includes apenetrating portion 21 at a center of a circular body portion 11, andtwelve teeth 31 extending radially from an outer side surface of thebody portion 11. Each of the teeth 31 has a distal end portion 41 with aprotrusion protruding in a circumferential direction and positioned atan outer end of each tooth 31.

The thin strip block 51 includes a fixedly joined portion 51B in whichthe nanocrystalline thin strips adjacent to each other in a laminationdirection (Z1-Z2 direction) are fixedly joined together. In the thinstrip block 51 illustrated in FIG. 2A, the fixedly joined portion 51B isdisposed in part of each of the distal end portions 41 of the four teeth31. In this embodiment, the fixedly joined portion 51B is a laser weldedportion.

As described above, the core assembly 50 illustrated in FIG. 1B isfabricated by arranging the multiple thin strip blocks 51 each of whichis prepared as an integrated body of the multiple nanocrystalline thinstrips 511. Because of using the thin strip block 51, failures, such asdamages, are less likely to occur in the nanocrystalline thin stripsthan in the case in which a laminated core is formed by laminating thenanocrystalline thin strips one by one. As a result, the quality of themagnetic core 100 obtained by forming the impregnated coating on thecore assembly 50 can be increased.

Furthermore, an overall size of the core assembly 50 can be easilyadjusted by changing the number of the arranged thin strip blocks 51,specifically the number of the laminated blocks, which are easy tohandle. Therefore, the magnetic cores 100 with different magneticcharacteristics can be easily fabricated. In addition, since themagnetic characteristics of the magnetic core 100 can be changed just bychanging the number of the laminated thin strip blocks in the coreassembly 50, change in the magnetic characteristics of the magnetic core100 can be realized without changing heat treatment conditions for thelaminate of the amorphous thin strips. Because, as described above, theheat treatment conditions need to be newly set whenever the number ofthe amorphous thin strips forming the laminate is changed, the magneticcore 100 according to this embodiment is superior in stability ofquality and productivity to a magnetic core that is manufactured byusing a method changing the number of the laminated thin strips in thelaminate.

When the fixedly joined portion 51B of the thin strip block 51 is thelaser welded portion as described above, the adjacent nanocrystallinethin strips 511 and 511 are electrically connected to each other throughthe fixedly joined portion 51B. Therefore, when an eddy current flows inthe magnetic core 100, a short circuit path of the eddy current isformed in units of the thin strip block 51. Thus, since the coreassembly 50 of the magnetic core 100 has a structure that the multiplethin strip blocks 51 are arranged, the short circuit path is formed inunits of the thin strip block 51. Accordingly, an eddy current lossgenerated in the magnetic core 100 can be relatively reduced. On theother hand, when the fixedly joined portion is disposed to fixedly joinall magnetic plates forming a laminated core together as in thelaminated core disclosed in International Publication No. 1999/21264,for example, a short circuit path is formed through the entirety of thelaminated core, and the eddy current loss is increased.

There are no limitations on a fixedly joining method used in forming thefixedly joined portion 51B. The adjacent nanocrystalline thin strips inthe thin strip block 51 may be fixedly joined with an adhesive. When thefixedly joined portion 51B is positioned in a region including sidesurfaces of the nanocrystalline thin strips 511, the fixedly joinedportion 51B may be cut portions of the nanocrystalline thin strips 511.In a practical example of such a case, the fixedly joined portion 51B isa fusion cut portion. FIG. 3A illustrates one example of the fixedlyjoined portion 51B disposed in the thin strip block 51 and representsthe case (fusion cutting) in which cutting (represented by a cuttingmark region 51C) and welding (represented by the fixedly joined portion51B) of the laminate of the nanocrystalline thin strips 511 areperformed at the same time. FIG. 3B illustrates another example of thefixedly joined portion 51B disposed in the thin strip block 51 andrepresents the case in which the fixedly joined portion 51B is formed bypartly welding cut surfaces of the laminate of the nanocrystalline thinstrips 511 together.

The core assembly 50 illustrated in FIG. 1B includes a shift-arrangedthin strip block group including a portion in which respective fixedlyjoined portions 51B, 52B, 53B, 54B, and 55B of the five thin stripblocks 51, 52, 53, 54, and 55 arrayed along a first direction (Z1-Z2direction) are not aligned in the first direction (Z1-Z2 direction). Asillustrated in FIG. 2B, the thin strip block 51 includes four fixedlyjoined portions 51B that are positioned at the protrusions 42 in thedistal end portions 41 of the teeth 31 and that are arranged in everythird tooth of the twelve teeth 31 of the thin strip block 51. Moreover,in two adjacent thin strip blocks (for example, the thin strip blocks 51and 52) in the core assembly 50, the two fixedly joined portions 51B and52B are not aligned in the first direction (Z1-Z2 direction). With thethin strip blocks 51, 52, 53, 54, and 55 arranged in the core assembly50 as described above, even when the fixedly joined portions 51B, 52B,53B, 54B, and 55B have different magnetic properties from otherportions, it is expected that spatial variations in the magneticcharacteristics of the core assembly 50 are less likely to occur.

While, in the core assembly 50 illustrated in FIG. 1B, the fixedlyjoined portion 51B of one thin strip block 51 in the core assembly 50 isarranged not to align with the fixedly joined portion 52B of anotherthin strip block 52 adjacent to the one thin strip block 51 in the firstdirection (Z1-Z2 direction) as described above, the present invention isnot limited to that case. FIGS. 4A, 4B, and 4C illustrates modificationsof the core assembly included in the magnetic core according to theembodiment of the present invention. Like a core assembly 501illustrated in FIG. 4A, the fixedly joined portions of the adjacent thinstrip blocks may be aligned in the first direction (Z1-Z2 direction). Inthis case as well, there is magnetic continuity between the two adjacentthin strip blocks, but there is no electrical continuity therebetween.Accordingly, the short circuit path in the core assembly 501 is formedin units of each of the thin strip blocks 51, 52, 53, 54, and 55.

In a core assembly 502 illustrated in FIG. 4B, unlike the core assemblyin FIG. 4A, the fixedly joined portion is not disposed in an outermostside surface of the core assembly 502 and is disposed in a side surfacepositioned on an inner side than the outermost side surface. Morespecifically, in the core assembly 502, the fixedly joined portions 51B,52B, 53B, 54B, and 55B are disposed in respective one side surfaces ofthe protrusions 42 in the distal end portions 41 of the teeth 31 in thecircumferential direction. In a magnetic circuit of a magnetic componentin which the magnetic core 100 including the core assembly 502 is used,a magnetic path is set to penetrate through the outermost side surfaceof the core assembly 502 in some cases. In those cases, if the fixedlyjoined portion is disposed in the outermost side surface, there is apossibility that the penetration of the magnetic path through thefixedly joined portion may affect characteristics of the magneticcomponent (for example, rotation characteristics of a motor). In thecore assembly 502, since the fixedly joined portion is not disposed inthe outer side surface of the protrusion 42 corresponding to theoutermost side surface of the core assembly, it is expected that themagnetic characteristics of the magnetic core 100 including the coreassembly 502 are less likely to be affected by the fixedly joinedportion.

In a core assembly 503 illustrated in FIG. 4C, the fixedly joinedportion 51B is disposed in an outer side surface of the body portion 11,the outer side surface being positioned in a space (corresponding topart of a slot SL of the magnetic core 100) between two adjacent teeth31 of the thin strip block 51. When the fixedly joined portion 51B isdisposed in the above-mentioned position, influences caused by theformation of the fixedly joined portion 51B upon the thin strip block 51can be made smaller than in the case of disposing the fixedly joinedportion 51B in part of the tooth 31. For example, when the fixedlyjoined portion 51B is formed in part of the tooth 31 by laser welding,there is a possibility that the tooth 31 may be partly deformed(solidified after melting) due to heat applied during the laser welding.On the other hand, in the case of the core assembly 503, because of thefixedly joined portion 51B being disposed in the body portion 11, evenif deformation occurs with the formation of the fixedly joined portion51B by the laser welding, the influences of the fixedly joined portion51B upon the magnetic characteristics of the magnetic core 100 can bemade smaller than in the case of forming the fixedly joined portion 51Bin part of the tooth 31.

In this embodiment, the nanocrystalline thin strip 511 is a thin stripmade of a nanocrystal-containing alloy material that is obtained bynano-crystallizing an amorphous thin strip made of an amorphous alloymaterial with heat treatment. More specifically, a nanocrystal containedin the nanocrystalline thin strip has a bcc-Fe phase as a main phase. Asdescribed later, the nanocrystalline thin strips 511 forming the thinstrip block 51 are obtained by heat-treating the laminate of theamorphous thin strips corresponding to the thin strip block 51 at atime.

A thickness of the thin strip block 51 is set to a value at which thenanocrystalline thin strips 511 can be produced from the amorphous thinstrips with the heat treatment. As a thickness of the laminate of theamorphous thin strips increases, heat generated due to crystallizationof the amorphous thin strips is harder to be released to the outside ofthe laminate, and controllability of the heat treatment reduces. Fromthe viewpoint of causing the heat treatment to progress properly,therefore, an upper limit is preferably set for the thickness of thethin strip block 51. On the other hand, because the nanocrystalline thinstrip 511 produced with the heat treatment is hard and brittle, thelaminate produced with the heat treatment preferably includes a certainnumber of the laminated nanocrystalline thin strips 511 from theviewpoint of increasing ease of handling. In consideration of the abovepoint, a lower limit is preferably set for the thickness of the thinstrip block 51.

In an example not intended to impose any limitations, the thickness ofthe thin strip block 51 is preferably 3 mm or less and more preferably 2mm or less in some cases. In addition, the thickness of the thin stripblock 51 is preferably 200 μm or more and more preferably 500 μm or morein some cases.

There are no limitations on a manufacturing method for the magnetic core100 according to this embodiment, but the magnetic core 100 can bemanufactured with high productivity when the following method is used tomanufacture the magnetic core 100. FIG. 5 is a flowchart illustratingone example of the manufacturing method for the magnetic core accordingto the embodiment (first embodiment) of the present invention.

As illustrated in the flowchart of FIG. 5 , a ribbon of amorphous thinstrip is first fabricated by, for example, a single-roll method (stepS101). The obtained ribbon of amorphous thin strip is cut into thinstrips in units of a proper length, and stamping is performed on each ofthe obtained thin strips, whereby a stamped member having a shapeillustrated in FIG. 2B in the plan view (when viewed from the Z1-Z2direction) is obtained (step S102). Thus-obtained multiple stampedmembers are laminated one above another, and a laminate is obtained(step S103). Because the amorphous thin strip has higher toughness thanthe nanocrystalline thin strip after the heat treatment as describedabove, chipping or other damages of the thin strips are less likely tooccur even when lamination work is performed.

A block-forming step of laser-welding an outer side surface of theobtained laminate at multiple locations is performed, and a block bodyis obtained (step S104). Heat treatment is performed on the obtainedblock body, and the thin strip block 51 is obtained (step S105). Asdescribed above, the heat treatment conditions are set such thatcrystallization properly progresses in all the amorphous thin stripsforming the block body, and that failures (for example, generation ofunnecessary matters, such as chemical compounds, and burning) caused bythe heat generated due to the crystallization are properly suppressed.

The multiple thin strip blocks 51 obtained with the heat treatment arelaminated one above another, and the core assembly 50 illustrated inFIG. 1B is obtained. At that time, rotary lamination of rotating,relative to one thin strip block 51, another thin strip block 52adjacent to the former about a center axis of the penetrating portion 21is performed such that the adjacent fixedly joined portions (forexample, the fixedly joined portion 51B and the fixedly joined portion52B) are not aligned in the first direction (Z1-Z2 direction) (stepS106).

Secondary heat treatment is performed on the core assembly 50 asrequired (step S107), and impregnation coating is performed on the coreassembly 50 (step S108), whereby the magnetic core 100 is obtained.After the impregnation coating, shape adjustment such as deburring isperformed as required in some cases (step S109).

A method of efficiently manufacturing the thin strip blocks 51 includedin the core assembly 502 illustrated in FIG. 4B, the method including astep of heat-treating core thin strip segments 300 at the same time,will be described below with reference to FIGS. 6, 8A, 8B, 8C, 9A, 9B,and 9C. FIG. 6 is a flowchart illustrating another example of themanufacturing method for the magnetic core according to the embodimentof the present invention. FIG. 8A is an explanatory view of amanufacturing process for a hoop material made of a ribbon of amorphousthin strip to form nanocrystalline thin strips included in the magneticcore according to the embodiment of the present invention. FIG. 8B is anexplanatory view illustrating a configuration of the hoop material madeof the ribbon of amorphous thin strip and manufactured by themanufacturing process illustrated in FIG. 8A. FIG. 8C is an explanatoryview illustrating a stamped section of the hoop material made of theribbon of amorphous thin strip, illustrated in FIG. 8B. FIG. 9Aillustrates a coupled laminate that is obtained after dividing the hoopmaterial made of the ribbon of amorphous thin strip, illustrated in FIG.8B, into smaller parts. FIG. 9B is an explanatory view of heat treatmentof the coupled laminate illustrated in FIG. 9A. FIG. 9C illustrates anarrangement of heat treatment apparatuses used in the heat treatmentillustrated in FIG. 9B.

In the manufacturing method illustrated in the flowchart of FIG. 6 , theribbon of amorphous thin strip is first fabricated by, for example, thesingle-roll method (step S201) in a like manner as in the manufacturingmethod illustrated in the flowchart of FIG. 5 . With the obtained ribbonof amorphous thin strip having higher toughness than the nanocrystallinethin strip, the obtained ribbon of amorphous thin strip is coiled into aroll (amorphous roll 201).

Then, a hoop material 205 is fabricated by stamping (step S202). FIG. 8Aillustrates a roll-to-roll method of fabricating the hoop material 205.The ribbon of amorphous thin strip 202 is unrolled from the amorphousroll 201 in one direction (specifically, toward an X1 side in an X1-X2direction), and the stamping is performed on the ribbon of amorphousthin strip 202 with stamping dies (an upper die 203 and a lower die204).

As illustrated in FIG. 8B, the obtained hoop material 205 includesstamped sections 350 each including the core thin strip segment 300 thatfinally becomes a substantial constituent member of the magnetic core100, a base material segment 211 that extends in an in-plane directionof the core thin strip segment 300 (specifically, in the X1-X2direction), and tie sticks 212 that connect the core thin strip segment300 and the base material segment 211. The stamped sections 350 arearranged side by side in an extension direction of the base materialsegment 211 (in the X1-X2 direction). Positioning holes (positioningportions 213) are formed in the base material segment 211.

As illustrated in FIG. 8C, a shape of the core thin strip segment 300 ofthe stamped section 350 in the plan view (when viewed from the Z1-Z2direction) is similar to that of the thin strip block 51. Morespecifically, the core thin strip segment 300 includes a penetratingportion 320 formed at a center of a circular body portion 310, andtwelve teeth 330 extending radially from an outer side surface thereof.Each of the teeth 330 has a distal end portion 340 with a protrusion 341protruding in a circumferential direction and positioned at an outer endof each tooth 330. As illustrated in FIG. 8C, some of the tie sticks 212are connected to the protrusions 341 protruding in the circumferentialdirection (Y1-Y2 direction) in the distal end portions 340 of the twoteeth 330 that extend along the X1-X2 direction. Some other of the tiesticks 212 are connected to the protrusions 341 protruding in thecircumferential direction (X1-X2 direction) in the distal end portions340 of the two teeth 330 that extend along the Y1-Y2 direction. Thus,cut portions CP of the tie sticks 212 are not positioned in connectionwith the outermost side surfaces of the distal end portions 340. In thethin strip block 51 obtained using the stamped section 350 illustratedin FIG. 8C, therefore, the fixedly joined portions 51B (namely, thecutting mark regions 51C) are not positioned in an outermost sidesurface of the thin strip block after the cutting as illustrated in FIG.4B.

Regardless of whether a cutting method is laser cutting or mechanicalcutting, a crystal state in the cutting mark region 51C may be changedfrom that in other regions. This raises a possibility that the magneticcharacteristics of the magnetic core 100 in a portion in which thecutting mark region 51C is positioned may become different from those inother portions. Accordingly, when the magnetic path in the magneticcircuit of the magnetic component including the magnetic core 100 passesthrough the cutting mark region 51C, there is a possibility that themagnetic characteristics may be changed in the cutting mark region 51Cand hence stability of the magnetic characteristics of the magneticcomponent may be affected. The resulting influence can be minimized byoptimizing the cutting method. In the magnetic circuit of the magneticcomponent using the magnetic core 100 that includes the thin strip block51, the magnetic path passes while penetrating the outermost sidesurface of the thin strip block 51 in some cases. However, since thecore assembly 502 illustrated in FIG. 4B is obtained by using thestamped section 350 illustrated in FIG. 8C, for example, the possibilityof the magnetic path in the magnetic circuit of the magnetic componentpassing through the cutting mark region 51C can be further reduced.

The hoop material 205 obtained by the stamping is coiled into a rolledmaterial 206. Then, the hoop material 205 is unrolled from the rolledmaterial 206 and is cut into smaller parts, whereby a coupled member 251including a predetermined number (for example, three) of the stampedsections 350 coupled together is obtained (step S203). As illustrated inFIG. 9A, thus-obtained multiple coupled members 251 are laminated oneabove another in the Z1-Z2 direction, and a coupled laminate 360 isobtained (step S204). Here, by utilizing the positioning portions 213 ineach of the coupled members 251, the coupled members 251 can be easilylaminated in the Z1-Z2 direction without touching the core thin stripsegments 300.

Then, heat treatment of the obtained coupled laminate 360 is performed(step S205). As illustrated in FIGS. 9B and 9C, multiple sets of heattreatment apparatuses 395 and 396 are prepared corresponding to thenumber of the laminates of the core thin strip segments 300 included inthe coupled members 251 forming the coupled laminate 360, and thelaminates of the core thin strip segments 300 are sandwichedrespectively between the sets of the heat treatment apparatuses 395 and396 in a lamination direction of the coupled laminate 360 (in the Z1-Z2direction). The heat treatment apparatuses 395 and 396 are to controltemperature of the core thin strip segments 300 and include,respectively, heat reservoirs 370 and 371 that have a substantiallycolumnar shape and that come into direct contact with the core thinstrip segments 300, and heater blocks 390 and 391 that heat the heatreservoirs 370 and 371. Thus, the heat treatment apparatuses 395 and 396have not only the function of applying heat to the core thin stripsegments 300, but also the function of receiving heat from the core thinstrip segments 300. Since the multiple sets of the heat treatmentapparatuses 395 and 396 are disposed as described above, conditions ofthe heat treatment applied to the laminates of the core thin stripsegments 300 included in the coupled laminate 360 can be held equal. Theheat treatment conditions are set such that the crystallization properlyprogresses in all the amorphous thin strips forming the core thin stripsegments 300 in the coupled laminate 360, and that failures (forexample, generation of unnecessary matters, such as chemical compounds,and burning) caused by the heat generated due to the crystallization areproperly suppressed.

With the heat treatment performed as described above, the amorphous thinstrips forming the core thin strip segments 300 in the coupled laminate360 are crystallized and turn to the nanocrystalline thin strips 511.Then, laser fusion cutting is performed on portions (cut portions CP) ofthe protrusions 341 connected to the tie sticks 212 to separate eachlaminate of the core thin strip segments 300 (the nanocrystalline thinstrips 511) and to fixedly join the nanocrystalline thin strips 511forming the separated laminate together, whereby the thin strip block 51illustrated in FIG. 4B is obtained (step S206). Thus, the fixedly joinedportion 51B of the thin strip block 51 manufactured by the manufacturingmethod illustrated in the flowchart of FIG. 6 is also the cutting markregion 51C.

Thereafter, as in the steps illustrated in FIG. 5 , the rotarylamination is performed (step S207), and the secondary heat treatment isperformed (step S208) as required, whereby the core assembly 50illustrated in FIG. 1B is obtained. Furthermore, the impregnationcoating is performed (step S209), and the shape adjustment is performed(step S210) as required, whereby the magnetic core 100 illustrated inFIG. 1A is obtained.

FIG. 10A is an explanatory view illustrating a modification of the heattreatment of the coupled laminate illustrated in FIG. 9B, and FIG. 10Bis a plan view illustrating a shape of a heating member used in the heattreatment illustrated in FIG. 10A.

When the heat reservoirs 370 and 371 included in the heat treatmentapparatuses 395 and 396 have the substantially columnar shape asillustrated in FIG. 9B, the cut portions CP (see FIG. 8C) come intodirect contact with the heat reservoir 370 as illustrated in FIG. 9C. Inthe coupled laminate 360 after the heat treatment step (step S205),therefore, the cut portions CP are also heat-treated and crystallized.Accordingly, there is a possibility that cutting workability may bereduced in the cut portions CP. As described above, the possibility ofthe magnetic path passing through the protrusions 341 to which the cutportions CP are connected is low. However, if the cutting workability isreduced, this may reduce uniformity in shape of the cutting mark regions51C and may affect retention of shape quality of the thin strip block 51in some cases.

When, as illustrated in FIG. 10A, a shape of each of heat reservoirs370A and 371A in the plan view (when viewed from the Z1-Z2 direction)corresponds to the shape of the core thin strip segment 300 in the planview, a portion of the tie stick 212, the portion being connected to theprotrusion 341 of the distal end portion 340, is not heat-treated in theheat treatment step (step S205), and the amorphous alloy remains there.Accordingly, the cut portion CP has good cutting workability in thecoupled laminate 360 after the heat treatment, and the shape quality isless apt to reduce even when, as illustrated in FIG. 4B, the fixedlyjoined portion 51B is positioned in the side surface of the protrusion341 of the distal end portion 340 of the thin strip block 51.

While the laser fusion cutting is used in the manufacturing methodillustrated in FIG. 6 to perform the cutting step and the block-formingstep at the same time, those steps may be performed as separate steps.FIG. 7 is a flowchart illustrating still another example of themanufacturing method for the magnetic core according to the embodimentof the present invention.

Comparing with the flowchart illustrated in FIG. 6 , the flowchartillustrated in FIG. 7 is different in that the “separation-cutting andblock-forming” step of the step S206 is divided into aseparation-cutting step (step S206A) and a block-forming step (stepS206B). In this case, the separation-cutting step is performed by, forexample, mechanical cutting, and the block-forming step is performed,for example, by laser welding. Furthermore, in the flowchart illustratedin FIG. 7 , comparing with the flowchart illustrated in FIG. 6 , theheat treatment step (step S205) is performed after the block-formingstep (step S206B). When a portion made of the amorphous alloy issubjected to the heat treatment step (step S205), the amorphous alloy isnano-crystallized, and the cutting workability in such a portion isreduced. Thus, when the separation-cutting (step S206A) is performedbefore the heat treatment step (step S205), good cutting workability canbe easily ensured for the tie stick 212. Moreover, when the amorphousthin strip is crystallized with the heat treatment and turns to thenanocrystalline thin strip 511, the thin strip becomes brittle, and easein handling the thin strip is reduced. However, by performing theblock-forming step (step S206B) before the heat treatment step (stepS205), easy handling can be ensured because a product obtained with theheat treatment is the thin strip block 51 in which the nanocrystallinethin strips 511 are laminated and fixedly joined together.

FIG. 11A is a plan view illustrating an example of a thin strip blockmanufactured by the manufacturing method illustrated in the flowchart ofFIG. 7 . FIG. 11B is an explanatory view illustrating a fixedly joinedportion of the thin strip block illustrated in FIG. 11A. The thin stripblock 510 illustrated in FIGS. 11A and 11B includes cutting residues 214at outer ends of the distal end portions 41 of the teeth 31. The cuttingresidues 214 are residues after the cutting when the tie sticks 212 arecut in the cut portions CP in the separation-cutting step (step S206A).In the thin strip block 510 illustrated in FIGS. 11A and 11B, as in thecore assembly 503 illustrated in FIG. 4C, the fixedly joined portion 51Bis formed by the laser welding in the outer side surface of the bodyportion 11, that outer side surface defining the space corresponding tothe slot SL.

FIG. 12A is a plan view illustrating a shape of an amorphous thin stripto form a core assembly included in a magnetic core according to anotherembodiment (second embodiment) of the present invention. FIG. 12Billustrates a shape of a thin strip block formed using the amorphousthin strip illustrated in FIG. 12A. FIG. 13A illustrates a ring assemblyincluding the thin strip blocks each illustrated in FIG. 12B, and FIG.13B illustrates a core assembly obtained by further combining the ringassemblies each illustrated in FIG. 13A.

In a core assembly 90 according to the second embodiment of the presentinvention, thin strip blocks 70 are arranged in order not only in alamination direction (Z1-Z2 direction) of nanocrystalline thin strips 60forming each of the thin strip blocks 70, but also in a directiondifferent from the lamination direction.

As illustrated in FIG. 12A, the nanocrystalline thin strip 60 accordingto the second embodiment includes a body portion 61 in a shape similarto one of quarters dividing a circular ring, a projection 62 projectingfrom the body portion 61 in a circumferential direction of the circularring, a recess 63 recessed into the body portion 61 in thecircumferential direction of the circular ring, and a tooth 64projecting from an inner circumferential side of the circular ringtoward a center of the circular ring. The projection 62 and the recess63 have engageable shapes such that one nanocrystalline thin strip 60can be coupled to another one.

A thin strip block 70 including fixedly joined portions 70B is obtainedby fixedly joining, into an integral unit, a laminate includingnanocrystalline thin strips 601 laminated one above another along athickness direction (Z1-Z2 direction). The thin strip block 70 includesan engagement projection 71 formed by the projections 62 of thenanocrystalline thin strips 60 and an engagement recess 72 formed by therecesses 63 of the nanocrystalline thin strips 60 such that one thinstrip block 70 can be engaged with another thin strip block 70.

As illustrated in FIG. 13A, the core assembly 90 according to thisembodiment includes a ring assembly 80 that is formed by engaging fourthin strip blocks 70 with each other at engagement portions 80C and thathas an annular shape in its entirety. A direction in which the thinstrip blocks 70 are arrayed in the ring assembly 80 is different fromthe lamination direction (Z1-Z2 direction) of the nanocrystalline thinstrips 60. Furthermore, as illustrated in FIG. 13B, the core assembly 90is constituted by laminating multiple ring assemblies (three ringassemblies 81, 82, and 83 in FIG. 13B) one above another. Fixedly joinedportions 81B, 82B, and 83B in the core assembly 90, given by the fixedlyjoined portions 70B of the thin strip blocks 70, are aligned in thelamination direction (Z1-Z2 direction). However, since the core assembly90 is electrically separated for each of the thin strip blocks 70, theshort circuit path is restricted within each thin strip block 70. As aresult, an eddy current loss in the magnetic core including the coreassembly 90 is less apt to increase.

FIG. 14A is an external view of a motor that is an example of a magneticproduct in which a magnetic component including the magnetic coreaccording to the embodiment of the present invention is used. FIG. 14Bis an external view of a rotor that is one of magnetic componentsincluded in the motor illustrated in FIG. 14A. FIG. 14C is an externalview of a stator that is another one of the magnetic components includedin the motor illustrated in FIG. 14A. As illustrated in FIG. 14A, themotor 700 includes a motor body 701 in a cylindrical shape, and arotating shaft 702 passing a center of a bottom surface of the motorbody 701 and protruding from the motor body 701 toward a Z1 side in theZ1-Z2 direction.

The rotor 710 illustrated in FIG. 14B is disposed inside the motor body701 to be rotatable about a rotation axis extending in the Z1-Z2direction. The rotor 710 includes a rotor body 711 in a hollow columnarshape with one of bottom surfaces (on the Z1 side in the Z1-Z2direction) being open, and the rotating shaft 702 fixed to a centralportion of the other bottom surface (on a Z2 side in the Z1-Z2direction) of the rotor body 711. Multiple magnets 712 are arranged onan inner wall of the rotor body 711 side by side in a circumferentialdirection.

The stator 720 in a columnar external shape is disposed between therotor body 711 and the rotating shaft 702 of the rotor 710. The stator720 is composed of the magnetic core 100 according to the embodiment ofthe present invention, and coils 721 wound around the teeth 30 of themagnetic core respectively. The rotating shaft 702 is inserted throughthe through-hole 20 of the magnetic core 100. The magnets 712 of therotor 710 are disposed on the inner wall of the rotor body 711 to facethe distal end portions 40 of the teeth 30 of the magnetic core 100 inone-to-one correspondence.

The magnetic core 100 according to the embodiment of the presentinvention has good magnetic characteristics because the core assembly 50including the thin strip blocks 51 laminated one above another, each ofthe thin strip blocks 51 being the laminate of the nanocrystalline thinstrips 511 fixedly joined together in the fixedly joined portions 51B,is firmly integrated by the impregnated coating. More specifically, thethin strip blocks 51 included in the core assembly 50 are magneticallyconnected but are not electrically connected, and hence the eddy currentloss is small. Furthermore, in the case of the magnetic core 100including the core assembly 502 (see FIG. 4B), since the fixedly joinedportion 51B is not disposed in the outermost side surface of the distalend portion 41, the magnetic circuit in the motor 700 is easilystabilized. It is therefore expected that, particularly, rotationcharacteristics of the motor 700 are stabilized.

The above embodiments are described with intent to make easierunderstanding of the present invention and not to limit the presentinvention. Thus, individual elements disclosed in the above-describedembodiments are purported to include all of design changes andequivalents falling within the technical scope of the present invention.

1. A magnetic core comprising: a core assembly including a plurality of thin strip blocks assembled together, each of the plurality of thin strip blocks being a laminated body formed of a plurality of nanocrystalline thin strips made of a nanocrystal-containing alloy material, wherein each of the plurality of thin strip blocks includes fixing portions in which the plurality of nanocrystalline thin strips are joined to each other in a lamination direction of the laminated body.
 2. The magnetic core according to claim 1, wherein the fixing portions are provided on a side surface of the laminated body such that each fixing portion includes side surfaces of the nanocrystalline thin strips.
 3. The magnetic core according to claim 1, wherein the fixing portions are laser welded portions where the nanocrystalline thin strips are laser welded to each other portion.
 4. The magnetic core according to claim 1, wherein each nanocrystalline thin strip is formed by nano-crystallizing an amorphous thin strip made of an amorphous alloy material with a heat treatment, and wherein the thin strip block has such a thickness that the nanocrystalline thin strip is produced from the amorphous thin strip by the heat treatment.
 5. The magnetic core according to claim 4, wherein the thickness of the thin strip block is 3 mm or less.
 6. The magnetic core according to claim 1, wherein in the nanocrystalline thin strip contains a nanocrystal having a bcc-Fe phase as a main phase.
 7. The magnetic core according to claim 1, wherein the plurality of thin strip blocks are arranged along a first direction in such a manner that the fixing portions of the plurality of thin strip blocks are not aligned in the first direction.
 8. The magnetic core according to claim 1, further comprising: an impregnated coating covering the core assembly.
 9. A magnetic component comprising the magnetic core according to claim
 1. 10. The magnetic core according to claim 1, wherein the fixing portions electrically connect the plurality of the nanocrystalline thin strips within the thin strip blocks, while the plurality of the thin strip blocks are electrically separated from each other.
 11. The magnetic core according to claim 1, wherein the plurality of thin strip blocks are stacked on one another along a laminating direction of the plurality of nanocrystalline thin strips.
 12. The magnetic core according to claim 1, wherein the plurality of thin strip blocks are engaged with one another along a circumferential direction perpendicular to a laminating direction of the plurality of nanocrystalline thin strips. 